<template>
  <view>
    <my-search></my-search>
    <view class="scroll-view-container">
      <!-- 左侧的滑动区域 -->
      <scroll-view class="left-scroll-view" scroll-y :style="{height:wh+'px'}">
        <block v-for="(item,index) in cateList" :key="index">
          <view :class="['left-scroll-view-item', index==active?'active':'']" @click="changeActive(index)">
            {{item.cat_name}}
          </view>
        </block>
      </scroll-view>
      <!-- 右侧的滑动区域 -->
      <scroll-view scroll-y class="right-scroll-view" :scroll-top="scrollTop" :style="{height:wh+'px'}">
        <view class="cate-lv2" v-for="(item2,index2) in cateLevel2" :key="index2">
          <!-- 二级分类的标题 -->
          <view class="cate-lv2-title">
            /{{item2.cat_name}}/
          </view>
          <!-- 三级分类列表 -->
          <view class="cate-lv3-list">
            <view class="cate-lv3-item" v-for="(item3,index3) in item2.children" :key="index3" @click="goToGoodsList(item3)">
              <!-- 图片 -->
              <image :src="item3.cat_icon" mode=""></image>
              <!-- 文本 -->
              <text>{{item3.cat_name}}</text>
            </view>
          </view>
        </view>
      </scroll-view>
    </view>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        // 手机可用高度
        wh: 0,
        // 获取分类列表数据
        cateList: [],
        // 活跃的类
        active: 0,
        // 二级分类数据
        cateLevel2: [],
        // 解决切换一级分类，二三级分类不回到顶部
        scrollTop: 0
      };
    },
    methods: {
      async getCateList() {
        const {
          data: res
        } = await uni.$http.get('/api/public/v1/categories');
        if (res.meta.status != 200) {
          return uni.$showMsg()
        }
        this.cateList = res.message
        // 为二级分类赋值
        this.cateLevel2 = res.message[0].children
      },
      // 改变active
      changeActive(index) {
        this.active = index
        // 为二级分类重新赋值
        this.cateLevel2 = this.cateList[index].children
        // 解决切换一级分类，二三级分类不会到顶部的bug
        /* 
        下面的代码之所以写成三元表达式，是因为scrollTop一直为0无法触发事件
        */
        this.scrollTop = this.scrollTop === 0 ? 1 : 0
      },
      // 从三级分类跳转到详情页
      goToGoodsList(item3){
        uni.navigateTo({
          url:"/subpkg/goods_list/goods_list?cid="+item3.cat_id
        })
      }
    },
    onLoad() {
      // 通过uni-app里面的api获取系统信息
      const systemInfo = uni.getSystemInfoSync();
      // console.log(systemInfo)
      // 为wh窗口的可用高度动态赋值
      this.wh = systemInfo.windowHeight-50

      this.getCateList()
    }
  }
</script>

<style lang="scss">
  .scroll-view-container {
    display: flex;

    .left-scroll-view {
      width: 120px;

      .left-scroll-view-item {
        line-height: 60px;
        background-color: #F7F7F7;
        text-align: center;
        font-size: 12px;

        &.active {
          background-color: #ffffff;
          position: relative;

          &::before {
            content: '';
            display: block;
            width: 3px;
            height: 30px;
            background-color: #c00000;
            position: absolute;
            left: 0;
            top: 50%;
            transform: translateY(-50%)
          }
        }
      }
    }

    .right-scroll-view {
      .cate-lv2-title {
        text-align: center;
        font-size: 12px;
        padding: 15px 0;
        font-weight: bolder;
      }

      .cate-lv3-list {
        display: flex;
        flex-wrap: wrap;

        .cate-lv3-item {
          width: 33.33%;
          display: flex;
          flex-direction: column;
          justify-content: center;
          align-items: center;
          margin-bottom: 10px;

          image {
            width: 60px;
            height: 60px;
          }

          text {
            font-size: 12px;
          }
        }
      }
    }
  }
</style>
